3. General Structure of an Insect Antenna
• Insect antennae are segmented appendages.
•Antennae are generally borne on between and behind the two compound eyes.
•Insects generally have one pair of antennae.
•All insects except Protura have antennae.
•A typical insect antenna constitutes of following segments ̶
i. Scape: first proximal segment which is connected with head sclerite.
ii. Pedicel: second antennal segment.
iii. Flagellum: third and longest segment of antenna. Flagellum is also many
segmented. The sub-segments of flagellum are called Flagellomeres or Annuli.
5. 1. Setaceous (Bristle like):
Size of the segments decreases from base to apex. e.g.
Leafhopper, Dragonfly, Damselfly.
2. Filiform (Thread like):
Segments are usually cylindrical. Thickness of segments
remains same throughout. e.g. Grasshopper.
3. Moniliform (Beaded):
Segments are either globular or spherical with prominent
constriction in between e.g. Termite.
4. Serrate (Saw like):
Segments have short triangular projections on one side.
e.g. Longicorn bettle.
5. Unipectinate (Comb like):
Segments with long slender processes on one side. e.g.
Sawfly.
6. 6. Bipectinate (Double comb like):
Segments with long slender lateral processes on both
the sides e.g. Silkworm moth.
7. Clavate (Clubbed):
Antenna enlarges gradually towards the tip. e.g. Blister
beetle.
8. Capitate (Knobbed):
Terminal segments become enlarged suddenly. e.g.
Butterfly.
9. Lamellate (Plate like):
Antennal tip is expanded laterally on one side to form flat
plates. e.g. Lamellicorn beetle.
10. Aristate:
The terminal segment is enlarged. It bears a
conspicuous dorsal bristle called arista. e.g. House
fly.
7. 11. Stylate:
Terminal segment bear a style like process. e.g.
Horse fly, Robber fly.
12. Plumose (Feathery):
Segments with long whorls of hairs e.g. Male
mosquito.
13. Pilose (Hairy):
Antenna is less feathery with few hairs at the
junction of flagellomeres. e.g. Female mosquito.
14. Geniculate (Elbowed):
Scape is long; remaining segments are small and are
arranged at an angle to the first resembling an elbow
joint. e.g. Ant, weevil and honey bee.
15. Flabellate (Fan like):
Very small, third and subsequent segments with side
processes giving a fan like arrangements. e.g.
Strepsipterans/ stylopids, cedar beetles.
9. Coxa
Trochanter
Tarsus
Tarsal
Claw
Pre-tarsus
Tarsomer
e
General Structure of an Insect Leg
• Insect legs are segmented appendages.
•Legs are generally borne on both sides of the three thoracic segments (viz.
prothorax, mesothorax and metathorax).
•Insects have three pairs of leg.
•A typical insect leg constitutes of following
segments ̶
i. Coxa: first proximal leg segment which
is connected with thoracic pleuron.
ii. Trochanter: second leg segment b/w.
coxa and femur.
iii. Femur: third and stoutest segment of
leg.
iv. Tibia: fourth segment of leg which is
usually long and provided with
longitudinal spines.
v. Tarsus: fifth segment of leg which is
furthermore divided into 3-5 sub-
segments termed as ‘tarsomeres’.
vi. Pre-tarsus: the terminal segment of leg,
comprises of tarsal claws and leg pads.
11. 2. Cursorial (Running Leg):
Leg suited for running. Femur is not swollen. Legs are
long and slender.
Ex. All three pairs of legs of cockroach.
3. Saltatorial (Jumping Leg):
Femur is swollen and provided with strong muscles for
jumping. Trochanter is fused with femur.
Ex. Hind legs of grasshopper.
1. Ambulatorial (Walking Leg):
Simple type of leg, no modifications. Femur and tibia are long.
Ex. Fore leg and middle legs of grasshopper.
4. Scansorial (Clinging Leg):
Tibia is stout and modified into a thumb-like process,
suited for clinging.
Ex. All three pairs of legs of head louse.
5. Natatorial (Swimming Leg):
Femur, tibia and first four tarsomeres are broad and
flattened, provided with long hairs/setae. Legs are
suited for swimming.
Ex. Hind legs of water beetle.
12. 6. Fossorial (Digging Legs):
Femur is stout, tibia and tarsus provided with strongly
pointed tines. Leg suited for digging.
Ex. Fore legs of mole cricket.
7. Raptorial (Grasping Leg):
Coxae elongated. Femur stout and grooved, tibia fits inside
the femoral groove. Both femur and tibia are provided with
spines. Leg suited for capturing prey, no use in locomotion.
Ex. Fore legs of Preying Mantis.
8. Foragial Leg:
Fore and middle legs provided with long hairs for pollen
collection. Hind tibia has a shallow cavity for storing pollen. It
is known as ‘Pollen Basket’ or ‘Corbicula’.
Ex. Legs of worker honeybees.
9. Sticking Leg:
Pre-tarsus provided with a pair of pads/‘Pulvilli’ and a
median spine like ‘empodium’. Legs suited for sticking to
smooth surfaces.
Ex. All three pairs of legs of housefly.
10. Prolegs or Abdominal Legs:
2-5 pairs of short, fleshy, non-segmented legs are found
in the abdomen of caterpillars. Prolegs are provided
with small circlets of hooks at the tip, known as
‘crochets’.
